Urinary mutagenicity has been used in occupation and epidemiological studies for over two decades as a biomarker of exposure to genotoxic agents. Few studies have compared urinary mutagenicity to additional biomarkers determined among exposed groups. We have evaluated the relationship between urinary mutagenicity and other biomarkers in a cross-sectional study of15 workers exposed to the urinary bladder carcinogen benzidine (BZ, high exposure), 15 workers exposed to BZ-dyes (low exposure), and 13 unexposed controls in India. Urinary organics were extracted and evaluated for mutagenicity in the presence of S9 in the Salmonella strain YG1024, a frameshift strain that overproduces acetyltransferase. The results were compared to biomarker data from the same urine samples that included a metabolite biomarker (the sum of the urinary levels of BZ + N-acetylbenzidine + N,N'-diacetylbenzidine as measured by isotope dilution mass spectrometry) and a DNA adduct biomarker [a presumpti ve N-(3'-phosphodeoxyguanosin-8-yl)-N'-acetylbenzidine (C8dG-ABZ) DNA adduct in exfoliated urothelial cells]. The mean ( SE urinary mutagenicity (revertants/(mol of creatinine) of the low-exposure (BZ-dye) workers was 8.2 ( 2.4, which was significantly different from the mean of the controls (2.8 ( 0.7, P = 0.04) as was that of the mean of the high-exposure (BZ) workers . Urinary mutagenicity showed strong, positive correlations with urinary metabolites (r = 0.88, P < 0.0001) and the level of the presumptive C8dG-ABZ urothelial DNA adduct (r = 0.59, P = 0.0006). A strong association was found between tobacco use (bidi smoking) and urinary mutagenicity among the controls (r = 0.68, P = 0.01) but not among the exposed workers (r = 0.18, P = 0.11). This study confirms the ability of a biomarker such as urinary mutagenicity to detect low-dose exposures, identify additional genotoxic exposures among the controls, and correlate strongly with urinary metabolites and DNA adducts in human urinary bladder epithelia.